This invention relates to a hot air space heater that is adapted to blow hot air out of a whole hot air outlet provided at a front plate of a frame of the heater, and more particularly to a hot air space heater of which the frame can be reduced in depth.
A construction of a conventional hot air space heater is shown in FIG. 1 of Japanese Patent Application Laid-open Publication NO. 316052/1999. In this construction, a combustion chamber and a fuel tank are arranged side by side in a frame of the heater, and a hot air outlet extends from a region in front of the combustion chamber toward a front of a region in which the fuel tank is located so that hot or heated air can be blown out of the whole hot air outlet. This conventional hot air space heater employs a special duct structure in order to guide air fed by a fan provided on a rear side of the frame to the hot air outlet. The duct structure has a combustion chamber space including the combustion chamber becoming narrower toward the front, and an extended air feed space spreading laterally from a front region of the combustion chamber space toward a front region of the fuel tank. In addition, a front portion of an upper wall of the duct is inclined toward the hot air outlet. In this conventional duct structure, it is impossible to permit hot air to flow through the extended air feed space without constructing the combustion chamber space narrower toward the front and inclining the front portion of the upper wall of the duct toward the hot air outlet. However, employing these constructions requires a distance between the combustion chamber and the hot air outlet to be relatively long, resulting in an increased depth of the frame of the heater.
In a conventional hot air space heater shown in FIG. 2 of Japanese Patent Application Laid-open Publication No. 316051/1999, the aforementioned extended air feed space is provided and a guide plate is mounted on at least one of louvers arranged in the hot air outlet. This guide plate has a V-shaped cross-section and is fixed onto the louver so as to direct an opening of the guide plate toward the combustion chamber. This duct structure of the heater also requires the front portion of the upper wall of the duct to be inclined toward the hot air outlet. In this hot air space heater, strong air flow without turbulence is blown against the guide plate mounted on the louver in order to guide or turn part of hot air to the extended air feed space. This heater also requires a distance between the combustion chamber and the hot air outlet (or a depth of the frame) to be relatively long because the front portion of the upper wall of the duct must be inclined. Therefore, the depth of the frame can only be reduced to a limited dimension.
Like Japanese Patent Application Laid-open Publication No. 316052/1999, Japanese Patent Application Laid-open Publication No. 4224/2001 (EP 1,217,314 A1) shows a hot air space heater that employs a specially shaped duct structure in order to permit hot air to flow into an extended air feed space.
FIG. 1 of U.S. Pat. No. 6,295,937 shows an example of a conventional hot air space heater in which a heat exchanger is arranged above a combustion chamber. In this example, the heater heats air taken into a duct structure from an indoor air intake port provided on a rear side of a frame of the heater by making the air contact with an outer wall of the combustion chamber and the heat exchanger, and then blows the heated air out of a hot air outlet. In this heater, the hot air outlet is arranged lower than the indoor air intake port.
U.S. Pat. No. 6,325,060 discloses a hot air space heater which is so constructed that a plurality of heat-exchange pipes are arranged on a combustion chamber and that a heat-exchange chamber is arranged on these heat-exchange pipes.
A hot air space heater of the present invention comprises a frame having a front plate, a rear plate, a pair of side plates connecting said front and rear plates, and a top plate. An indoor air intake port is provided at the rear plate. A hot air outlet is provided at the front plate. The hot air outlet is formed so as to extend from a position in proximity to one of the side plates to a position in proximity to the other side plate in a lateral direction, and is positioned lower than the indoor air intake port. The heater also comprises a burner arranged in the frame in a manner to be close to one of the side plates rather than at a central portion of the frame, a combustion chamber arranged on and communicating with the burner, a heat exchanger arranged on an upper plate of the combustion chamber and communicating with the combustion chamber, and a duct structure having an air feed passage therein. The heater further comprises an indoor air convection fan arranged in the vicinity of the indoor air intake port to take in indoor air into the air feed passage.
The heat exchanger, for example, includes a plurality of heat-exchange pipes extending upward from the upper plate of the combustion chamber and an exhaust gas chamber arranged on and communicating with these heat-exchange pipes.
The hot air outlet has a first hot air outlet portion positioned in front of the upper portion of the combustion chamber and the heat exchanger, and a second hot air outlet portion laterally contiguous to the first hot air outlet portion and positioned in front of a region including an accessory-receiving space.
The duct structure includes a first side wall arranged adjacent to the one side plate; a second side wall facing the first side wall in the lateral direction so as to have the upper portion of the combustion chamber, a plurality of the heat-exchange pipes, and the exhaust gas chamber positioned therebetween and also facing the other side plate of the frame in the lateral direction so as to form the accessory-receiving space therebetween; a bottom wall positioned lower than the upper portion of the combustion chamber; a top wall having a main portion thereof positioned upper than the heat exchanger; and a front wall positioned between a front end of the top wall and the hot air outlet and longitudinally extending along the front plate. The second side wall includes a first side wall portion positioned on a side of the rear plate and extending along or juxtaposedly with the first side wall and a second side wall portion connecting to the first side wall portion and extending in the lateral direction so as to form an extended air feed space laterally spreading between the second side wall portion and the second hot air outlet portion.
In the present invention, an air guide is arranged in the duct structure. The air guide is arranged along the first outlet portion of the hot air outlet facing the upper portion of the combustion chamber so as to guide or turn part of air to be blown forward out of the first hot air outlet portion to the extended air feed space. Providing such air guide in the duct structure can guide or turn part of the air directed forward through the second hot air outlet portion to the extended air feed space, even when a distance from the upper portion of the combustion chamber and the heat exchanger to the hot air outlet is reduced. In other words, hot air blown against the air guide is reflected backward and then tends to flow toward the extended air feed space having a smaller air resistance. The air guide positively guides or turns the air flow to the extended air feed space. Thus, in accordance with the present invention, a sufficient amount of hot air can also be blown forward out of the second outlet portion of the hot air outlet corresponding to the extended air feed space.
A vertical dimension or height of the hot air outlet is preferably defined so as to be able to face both the upper portion of the combustion chamber and lower portions of a plurality of the heat-exchange pipes communicating with the combustion chamber. This enables sufficient heat exchange at the heat exchanger.
The air guide is preferably formed so as to have a plate-like member extending toward the extended air feed space along the first hot air outlet portion. Any support structure may be selected for the plate-like member. The plate-like member may be supported by the first or second side wall or the bottom wall of the duct structure. In these cases, the plate-like member is arranged in a manner to define a first air flow path between an upper edge of the plate-like member and the front wall of the duct structure and a second air flow path between a lower edge of the plate-like member and the bottom wall of the duct structure. This arrangement enables both hot air flowing downward along the front wall and hot air flowing directly to the hot air outlet through between a plurality of the heat-exchange pipes to blow out of the first air flow path. Hot air flowing around the upper portion of the combustion chamber and directly into the second air flow path, and most of hot air flowing around the heat-exchange pipes and blown against the plate-like member get together and flow out of the second air flow path. An interval size (distance) between the lower edge of the plate-like member and the bottom wall is defined so as to permit hot air passing through the second air flow path to flow out forward. Specifically, the lower edge of the plate-like member is arranged in proximity to the upper plate of the combustion chamber. In a case where at least part of the hot air flowing out of the first air flow path goes downward, this flow will be re-directed or turned forward rather than downward by means of the hot air flowing forward out of the second air flow path. As a result, hot air can reach a user of the heater sitting in front of the heater.
It is preferable to arrange the plate-like member so that one end thereof is fixed onto the first side wall of the duct structure and the other end is positioned on a side of the extended air feed space. In this arrangement, an air flow path is not formed between the first side wall and the plate-like member, thereby guiding most of hot air blown against the plate-like member to the extended air feed space along the plate-like member. Also, since no support structure exists in the second air flow path, the rate of hot air flowing out of the second air flow path will not be decelerated.
The second side wall portion of the second side wall may extend substantially in parallel to the hot air outlet. This can simplify a shape of the second side wall of the duct structure.
The first side wall and the first side wall portion of the second side wall of the duct structure may be provided each with an air-blocking plate that prevents air fed by the fan from flowing directly into the second air flow path by reducing a gap formed between an outer circumferential surface of the upper portion of the combustion chamber and an inner surface of the first side wall, and a gap formed between the outer circumferential surface of the upper portion of the combustion chamber and an inner surface of the first side wall portion of the second side wall (theoretically, the gap size may be reduced to zero). As these gaps become larger, air from the fan will be fed through the gaps straight into the second air flow path. With this situation being kept, it will result in an extremely increased amount of hot air flowing out of the second air flow path, thereby reducing an amount of hot air flowing into the extended air feed space. However, providing an air-blocking plate substantially eliminates such air flowing from the fan directly into the second air flow path, which in turn prevents hot air flowing out of the second air flow path from increasing extremely. As a result, a sufficient amount of hot air can positively flow into the extended air feed space. When thus-formed gaps are very small, it is not necessary to provide an air-blocking plate.
In the duct structure, a boundary portion between the first and second side wall portions of the second side wall is preferably positioned on a front side of the air blocking plate and on a rear side of an front edge portion of the upper portion of the combustion chamber. This positioning widens an opening of a space positioned on a rear side of the air guide and communicating with the extended air feed space. Accordingly, air resistance against the extended air feed space becomes smaller than that against the second air flow path, thereby permitting a larger amount of hot air to flow into the extended air feed space, accelerating the hot air flowing forward out of the second outlet portion, and enabling the hot air to reach further than ever.